1. Field of the Invention
The present invention relates to a bulb photography control system for a camera for electrically acutating the camera and mechanically operating the shutter closing.
2. Description of the Prior Art
Until now, electronic shutter cameras having an electromagnetic release device for electromagnetically actuating the camera have utilized two systems for carrying out bulb photography, namely one for carrying out bulb photography electrically and another system for carrying out the bulb photography mechanically.
In the first system, for carrying out the bulb photography electrically actuation of the electromagnetic release device is accompanied by the aperture control mechanism and the quick return mirror control mechanism starting to operate, while, at the same time the tail or trailing shutter curtain holding magnet is brought into a hold state. When the aperture or the quick return mirror control mechanism has operated, the leading shutter curtain is made to start to run so as to start the exposure while the shutter is kept open. Then, along with the release operation of the release button the tail shutter curtain is made to run so as to terminate the exposure. When the tail shutter curtain runs or has run, the current supply to the control circuit of the camera is interrupted so as to bring the camera into the rest state.
In the second system for carrying out bulb photography mechanically, during the bulb photographing mode, the circuit and the mechanism are changed over in such a manner that instead of an electromagnetic release device, a mechanical release mechanism is used. The shutter is kept open by means of a mechanical tail shutter curtain holding mechanism operatively engaged with the release button. Along with the release operation of the release button the holding mechanism is released so as to allow the tail shutter curtain to start to run and terminate the photographing operation. Hereby, the changeover of the circuit is generally intended to interrupt the current supply to the control circuit of the camera.
However, in the first system for electrically carrying out bulb photography, the current runs through the tail shutter curtain holding magnet and its control circuit for the whole time during which bulb photography is carried out so that battery consumption is substantially increased. This increase is all the more considerable in case of a long time exposure, for example microscopic photography, close up photography, celestial body photography and so on. Further, when the above mentioned photography is carried out under low temperatures, the efficiency of the battery lowers, which makes operation all the more disadvantageous.
In the second system for mechanically carrying out bulb photography the electromagnetic and mechanical release mechanisms, and their change over mechanism, are necessary so that not only the construction inside of the camera which is spatially restricted becomes quite complicated so as to raise the manufacturing cost but also there is a difference between the feel of operation depending on whether the electromagnetic release or the mechanical release is used, which is disadvantageous.